Friday, September 14, 2007

2005 Robotic modelling reveals ancient hominid stride

Robotic modelling reveals ancient hominid stride

An ancient human ancestor once thought to have shuffled its way across the plains of Africa in fact walked upright much like modern man, a study of robotic models has revealed.

UK researchers built robot-based computer models of Australopithecus afarensis - a human ancestor that lived more than three million years ago.

They constructed the computer model using a fossilised A. afarensis skeleton known as "Lucy", recovered from Ethiopia in 1974. The researchers then added virtual muscle to their simulation and used genetic algorithms to "evolve" the optimal walking movement for the creature.

"We compared the model’s speed and stride length with that of modern humans," says team member Weigie Wang at the University of Dundee. "We conclude that they definitely would have walked bipedally."

The researchers also found that the model of locomotion produced in their simulations closely matched a set of fossilised footprints thought to have been left by A. afarensis in Laetoli, Tanzania, some 3.6 million years ago.

Darwinian code

Genetic algorithms employ the principles of Darwinian evolution to come up with an optimised - or "evolved" - solution to a problem. A population of algorithms is tested and the most effective selected for survival, while the least successful are killed off.

The surviving algorithms are then recombined and mutated and tested again. Over thousands of simulated generations, the population becomes well adapted to tackling the problem at hand. The approach has proven its worth in many fields, such as automated product design and computer network topologies.

The algorithms used to evolve the A. afarensis walking style corresponded to different configurations of muscle mass, length and positions on the bone. These were tested for energy efficiency in walking-motion simulations on the computer.

"This is interesting work," says Chris Stringer, an expert in paleoanthropology at the Natural History Museum in London, UK. "It brings in more information about the skeleton of A. afarensis."

But Stringer notes that some uncertainty remains over precisely which species of hominid created the Laetoli footprints. For example, some researchers have proposed that afarensis-like remains discovered in Kenya in 1999 – similar in age to “Lucy” – be classified as a separate species, called Kenyanthropus. "One of the unknowns at this time is species diversity," Stringer told New Scientist.

Journal reference: Journal of the Royal Society Interface (DOI: 10.1098/rsif.2005.0060)